02
Dec
Study Affirms that Organic Farming Improves Soil Health, Microbial Life, and Pathogen Resistance
(Beyond Pesticides, December 2, 2024) An international team of researchers has found that organic farming increases the quantity and diversity of crop plant microbiota, further safeguarding crops with enhanced pathogen resistance. Their recent study, published in Plants, People, Planet, builds on the legacy of decades of peer-reviewed research and centuries of agricultural systems that do not rely on toxic, petrochemical-based products (e.g., fertilizers, pesticides, etc.) as the driving force for agricultural productivity. As many analysts express concern that the incoming administration will increase the promotion of petrochemicals in domestic food production and eschew regulations to curtail their use, organic advocates and farmers remain committed to transforming agricultural and land management systems that reject chemical dependency, which is escalating the existential threats to biodiversity, public health, and the climate.
Goals, Methodology, and Background
The authors of this study are researchers at Université de Rennes, Université de Paris-Saclay, L’Institut Agro Rennes-Angers, European Society for Agronomy, France’s National Research for Agriculture (INRAE), and Nanjing Agricultural University in Nanjing, Jiangsu, China. The goal of this study was to compare the effects of organic with chemical-intensive agricultural plots on microbial life on winter wheat roots. Winter wheat was selected because of the projected increase in global demand and consumer interest in wheat products that are grown in environmentally responsible systems. The authors tested the four following hypotheses:
- “[O]rganic farming changes microbial community composition and species interactions and results in more diverse microbial assemblages than conventional farming ();
- [T]his effect is related to changes in management practices, soil properties, and/or plant diversity ();
- [C]hanges in microbiota affect host plant reproduction and resistance to pathogens (); [and]
- We expected responses to be more pronounced in May than in March due to the effects of the different farming systems during plant development that would increase divergences in microbiota composition.â€
The researchers conducted this study on forty winter wheat fields at “Zone Atelier Armorique,†also known as the Long-Term Socio-Ecological Research (LTSER) site in north-western France. Twenty of the fields are organically managed and the other twenty are not. The environmental and agronomic data includes surveys of the land management practices, soil, and plant and cultivar types. The bacterial and fungal microbiota were sampled from “six individual wheat plants in each field (40 fields) at two dates (mid-March—vegetative stage and the end of May—early reproductive stage of wheat).†Each sampling campaign, March and May, evaluated 240 samples. Wheat fitness is measured by the plant samples’ reproductive capacity and pathogen resistance, which was pulled from the 240 samples gathered in May, at which point they “had all completed their reproductive phase.†The authors state, “We then calculated the mean total number of seeds per field as the mean number of seeds of the six individual wheat plants [gathered from each field.]â€
“All the analyses were performed in 35 fields for fungi; in 34 fields for bacteria in March and in 29 fields for bacteria in May because information concerning agricultural management was lacking for three fields out of 40, and insufficient description of bacteria and fungi microbiota for one field out of 40 for bacteria in March; and for five fields out of 40 for bacteria in May. Consequently, only fields for which all variables were available were included in the analyses,†says the researchers. The bacteria tested in this study include Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes, Alphaproteobacteria, Deltaproteobacteria, and Gammaproteobacteria. Meanwhile, the fungi analyzed in this study include Ascomycota, Basidiomycota, Chytridiomycota, Glomeromycotina, and Zygomycota.
Results and Discussion
The researchers analyzed the effects of agricultural management practices, soil characteristics, and plant diversity on bacterial and fungal entities independent of one another before analyzing them in full. The bottom-line argument: “The present study provides a better understanding of the effect of organic farming on plant-associated microbiota and stresses the importance of soil characteristics and management in shaping microbiota composition and diversity. It also highlights the fact that plant seed production and resistance to pathogens are related with particular microbial assemblages. More specifically, Alphaproteobacteria and Glomeromycotina were seen to be key phyla in mediating wheat fitness, while also responding to environmental parameters.†In this study, Glomeromycotina has a statistically significantly higher degree of richness in organic fields in both March and May.
The researchers also found that the most significant richness of all bacteria and fungi is identified in organically managed farmland relative to conventional fields in the month of May. Soil properties, including carbon, nitrogen, pH level, organic matter content, and proportion of clay and coarse silt, do influence the bacteria and fungi composition of all fields regardless of when sampled.
“The positive effect of organic farming on microbial diversity was more pronounced in May than in March for both fungi and bacteria, while an early effect on bacterial composition was detected in March,†say the researchers. This is one of the study’s main conclusions,  which they attribute in part to “the cumulative effect of phytosanitary products and nitrogen inputs during crop growth.â€
“Indeed, under organic farming, no phytosanitary products are used on wheat, and nitrogen inputs are lower despite the use of organic manure () (). In all responding phyla, as expected, increasing nitrogen and phytosanitary inputs had a detrimental effect on species richness and shaped sequence-cluster composition (),†the researchers explain as the beneficial impacts of the low-to-zero input approach of organic farming systems.
Organic Farming as a Driver of Soil Health
There are numerous peer-reviewed studies highlighting the importance of organic farming practices and methods for biodiversity at all scales, from microbial to planetary health.
A 2024 study published in Agriculture, Ecosystems, and Environment finds the perpetual use of pesticide-coated seeds and tillage changed the composition of various beetle, spider, and other epigeal arthropod communities on New Hampshire farmland. In Rodale Institute’s landmark Farming Systems Trial – the longest-running, multidecade investigation comparing organic and chemical-intensive grain production in North American farmland – researchers arrived at the following outcomes (See Daily News here.):
- Organic systems achieve 3–6 times the profit of conventional production;
- Yields for the organic approach are competitive with those of conventional systems (after a five-year transition period);
- Organic yields during stressful drought periods are 40% higher than conventional yields;
- Organic systems leach no toxic compounds into nearby waterways (unlike pesticide-intensive conventional farming);
- Organic systems use 45% less energy than conventional ones; and
- Organic systems emit 40% less carbon into the atmosphere.
Researchers at Kansas State University corroborate some of the findings determined by Rodale Institute in a 2024 study published in Soil Science Society of America Journal, finding direct evidence that organic amendments (e.g., manure and compost) in a no-till agricultural system “facilitat[e] microbial diversity†that cycles plant-available nutrients. Organic banana production in Martinique are found to have 55% higher mean plant species richness and 79% greater soil weed cover in organic fields, according to a 2024 study published in Applied Soil Ecology. In the same study, the presence of earthworms, macrofauna, and other decomposers was much higher in organic fields, indicating the enhanced microbial life in organic farming systems. For additional Daily News coverage on soil microbial health and organic practices, see here, here, here, and here.
Call to Action
See the Action of the Week, Tell U.S. Department of Agriculture (USDA) to Expand Organic Dairy Product Promotion (ODPP) Program to All-Organic Lunches, to demand USDA and Congress mandate organic dairy products in the National School Lunch Program given the recent $15 million investment in ODPP through the Commodity Credit Corporation.
See Keeping Organic Strong to learn about the variety of issues that arise at statutorily mandated, biannual National Organic Standards Board (NOSB) meetings. Beyond Pesticides submits comments on all issues before the NOSB, and includes on our website guidance for the general public on engaging in the public input process to ensure the integrity of organic standards, as well as vital add-on labels such as Real Organic Project and Regenerative Organic Certified (Regenerative Organic Alliance).
All unattributed positions and opinions in this piece are those of Beyond Pesticides.Â
Source: Plants, People, Planet
